Automatic firing systems for gun perforators for wells



Aprll 12, 1955 w. E. KANADY 2,705,920

AUTOMATIC FIRING SYSTEMS FOR GUN PERFORATORS FOR WELLS Filed Sept. 11,1950 FIG. 3.

INVENTOR. William E.Kanady,

BYWW

A T TORNE Y.

United States Patent AUTOMATIC FIRING SYSTEMS FUR GUN PERFQRATORS FORWELLS William Edward Kanady, Housten, Tex., assignor, by mesneassignments, to Esso Research and Engineering Company, a corporation ofDelaware Application September 11, 1259, Serial No. 184,170

1 IL-aim. (Cl. 10221.8)

This invention relates to guns for perforating casing in oils wells orthe like and more particularly to automatic firing systems for suchguns.

Methods of perforating casing in oil wells are now common. Both bulletguns and those using shaped charges of explosive have come into generaluse.

It has recently been proposed to lower perforating guns through tubinginside the casing in an oil well. See for example the application ofTheodore A. Huber, Serial No. 133,025, filed December 15, 1949, forMethod of Completing and Repairing Oil Wells Where the use of a casingperforating gun capable of being run through tubing is required. Largesavings in time and cost in drilling can be efiected in this way ifeffective perforation can be accomplished.

The present invention relates to a firing system which is particularlyadapted for use in connection with guns which are to be lowered throughtubing in a well bore to perforate the casing beneath the lower end ofthe tubing. It can be used either with a bullet gun or with one usingshaped charges of explosive. The arrangement is such that a firing pinis released automatically when the gun passes out of the lower end ofthe tubing, a trigger being pulled or released at that time. Inaddition, if desired, slips may be actuated to grip the tubing andconnect the gun to the tubing automatically at the time of firing, orapproximately at that time, so that the gun can be retrieved through thetubing.

The objects of the invention will be apparent from the followingdescription, taken in connection with the accompanying drawings, inwhich:

Fig. 1 is a view in vertical cross-section of tubing in a well bore witha gun firing system constructed in accordance with the present inventionpassing downwardly therethrough.

Fig. 2 is a similar view showing a second embodiment of the invention.

Fig. 3 is a similar view showing a third embodiment of the invention.

Referring to the drawing in detail, it will be seen that in all threefigures, a section of well tubing is shown at 13. In each of thefigures, a different construction of trigger or firing system is shownat the top of a gun perforator body 14, only a fragmentary portion ofwhich is shown. The construction of the particular perforator gun hasnot been shown because, per se, it forms no part of the presentinvention. It may be of any construction, but is preferably of the typein which a flexible container is employed so that it may pass downthrough the tubing 13 even though the tubing is crooked or bent to someextent, as taught in the copending application of Earl Babcock, SerialNo. 184,166, filed on even date herewith.

As shown in Fig. l, the trigger system is contained within a housing 15which may be integrally connected to the top of the gun body 14. At theupper end of the housing 15, an enlarged head portion 16 may be providedwhich may come to rest upon a seating ring 17 secured to the tubing atthe bottom thereof, as by means of a shear pin 18.

Within the housing 15, there is a powder chamber 20 into which the upperend of the prima cord 21 may be brought, and which is provided with afiring cap 22. A firing pin 23 is mounted immediately above the cap 22on a piston 24 within a cylinder 25 and it is normally held away fromthe cap 22 by a compression coil spring 26; while a piston and cylinderhas been illustrated, ob-

2,705,920 7 Patented. Apr. 12, 1955 viously a diaphragm or bellowsarrangement would be the equivalent.

On the top of the piston 24 there is a stud 27 adapted to be gripped andheld against downward movement by the jaws 28 of a trigger consisting ofarms 29 pivoted at 30. The upper ends of the arms 29 are urged outwardlyat all times by a compression coil spring 31, so that the jaws 28 alwaystend to grip the stud 27 under the influence of the spring 31.

The operation of the firing system of Fig.1 is dependent upon thepresence of the seating ring 17 inside the tubing. When the assembly islowered down through the tubing 13, before the head 16 comes to rest onthe seating ring 17, the trigger arms 29 strike the ring 17 and theirupper ends are forced inwardly so that the jaws 28 release the stud 27.Since the well contains liquid when the gun is lowered into it, thepressure on top of the piston 24 is large, so that when the stud 27 isreleased, the piston 24 moves downwardly rapidly and causes the firingpin 23 to strike the cap 22 and fire the powder in the chamber 20,igniting the prima cord and setting off the guns below.

Because of the spring 26, there is no danger of the gun being firedaccidentally at the surface or" the ground since there is no liquidpressure on top of the piston 24 until the gun has been lowered into thewell. Hence even if the trigger arms 29 are struck accidentally inhandling the gun, it will not go Ofi.

After the gun of Fig. 1 has been fired, it may be retrieved by thefishing spear 32 on the top of the head 16 or it may be pumped to thebottom of the well by exerting pump pressure in the tubing to shear thepin 18.

The arrangement of Fig. 2 is similar in some respects to that of Fig. 1and similar parts have been similarly designated. This arrangement isnot dependent upon a seating ring in the tubing. The guns are firedautomatically when the gun passes out of the tubing and the design issuch that the assembly is not retrieved, after firing, but is dropped tothe bottom of the well bore.

The trigger arms 33 in the arrangement of Fig. 2 are different fromthose in Fig. 1 in that they cross on the pivot 39. The arms 33 are likea pair of pliers. Hence the spring 31 normally urges them intoengagement with the inside of the tubing 13. When the assembly leavesthe tubing, the arms 33 move outwardly and the stud 2"] is released tofire the guns. All that is necessary to operate the gun of Fi 2 is placeit in the tubing and let it fall or pump it to bottom. As it leaves thetubing it goes off.

The arrangement of Fig. 3 is like that of Fig. 2 in that the triggerarms move outwardly on firing but the mechanism is different and meanshas been added which make it possible for the gun to be retrievedthrough the tubing by a fishing tool. A marked advantage in thearrangements of Figs. 2 and 3 over that of Fig. 1 is that the tubing mayremain unobstructed. This is important because it enables a largerdiameter gun to be employed, and the diameter of the gun is veryimportant Where it must be run into the well through tubing.

Parts of Pig. 3 similar to those of Figs. 1 and 2 are similarlydesignated and their operation will be clear from what has been saidabove. In Fig. 3, the stud 3 5, on top of the piston 24 is slightlylonger than the studs 2:! of Figs. 1 and 2 and the lower surface of itshead is pered to rest upon the upwardly inclined iaws 35 of the triggerarms 36. Tension springs 37 tend to draw the arms 36 inwardly, but untilthe assembly passes out of the lower end of the tubing 13, they cannotmove inwardiy because their upper ends are held apart by a wedge 38 on astem 39.

The stem 39 may be rectangular in cross-section and the wedge 38 ismounted for limited sliding movement thereon as illustrated. Above thewedge 38, the stem 39 may be slotted transversely, as shown, toaccommodate the upper ends of trigger arms 36 when the springs 37 drawthem inwardly after the gun has been fired, the wedge 38 then being onthe lower end of the stem 39. The springs 37 are ofiset suificiently toallow the lower end of the stem 39 to pass between them.

A set of slips 40 are provided above the trigger arms 36 and these areadapted to be actuated by a slip body The stem 39 is urged downwardly bya compression.

coil spring 42 held between the slip body 41 and the upper interior wallof the housing 15. Thus the trigger arms 36' serve a double function inthat they hold the stud 34 against downward movement and they hold theslips 40 out of engagement with the tubing. When the trigger arms moveout of the lower end of the tubing, they are forced outwardly under theaction of the coil spring 42 and the wedge 38'snaps past the upper endsof the arms 36. The arms 36 can then move inwardly about their pivots43. When' they move outwardly they first release the stud 34, causingthe firing of the guns as outlined above. Theaction is such that theslips grip the tubing 13, and fix the gun with respect thereto, justafter the While only three embodiments have been shown and describedherein, it is obvious that various changes may be made without departingfrom the spirit of the invention or the scope of the annexed claim.

I claim:

In an automatic firing system for use with a gun adapted to be run intoa well through tubing to perforate casing beneath the tubing comprising,in combination, a housing adapted to be connected to the top of the gunbody; pressure responsive means carried by said housing, said pressureresponsive means carrying a firing pin; a firing cap disposed in thepath of said firing pin; trigger means comprised of a plurality of armspivoted in said firing of the guns, for the wedge 38 moves the upperends of the trigger arms 36 outwardly before the slips are set. As thewedge 38 passes the upper ends of the arms 36, it drops to the lower endof the stem 39 and the arms 36 move inwardly so that when the assemblyis retrieved, the arms can be pulled up into the tubing 13.

After the guns have fired, the assembly, or so much w of it as has notbeen destroyed on firing, may be retrieved through the tubing by afishing tool which may grip the fishing spear 44 attached to'the upperend of the stem 39. By pulling up on the stem 39, the slips areretracted inwardly 'at this time.

housing, said arms being adapted normally to restrain said pressureresponsive means against movement toward said cap; spring means biasingthe arms of said trigger means outwardly so as to cause said arms torelease automatically said pressure responsive means when said armsreach a point adjacent to the lower end of said tubing; a set of slipson said housing; and a slip body adapted to move said slips outwardly ofsaid-body on downward movement thereof, said slip body being biased downwardly by said spring means.

Hampton Apr. 3, 1951

